Typically, when a dipstick is installed in an engine, it extends through an opening provided towards the top of the engine, and through one or more portions of engine casing. For example, the dipstick may extend through a cam cover, a cylinder head, a cylinder block, and into a ladderframe casing. A free end of the dipstick is positioned in the oil contained in an oil pan at the bottom of the engine.
As a result of the required characteristics of the dipstick, such as its material properties and its elongated shape, it is particularly prone to bending and vibration. For example, where the portions of the engine casing are provided with simple through holes for the dipstick to pass through, potential noise vibration and harshness (NVH) issues may be experienced. For example, a portion of the dipstick may be free to vibrate, and possibly even resonate, during engine operation. Additionally, due to the proximity of the free end of the dipstick to the oil pan, the free end of the dipstick may vibrate and contact an interior wall of the oil pan, which can lead to a harsh rattling noise during operation of the engine.
In one example, the issues described above may be addressed by a system for an engine comprising an engine casing and a dipstick, the dipstick having a free end that extends into the engine casing when the dipstick is installed to the engine casing, wherein the dipstick is adapted such that the lowest natural frequency of the free end of the dipstick is above the highest operational frequency of the engine. At least one of the shape, configuration and mass distribution of the free end of the dipstick may be selected so that the lowest natural frequency of the free end of the dipstick is above the highest operational frequency of the engine. In this way, the frequency and orientation of the dipstick may be selected such that the noise vibration and harshness of the dipstick is reduced.
As one example, dipstick may contact portions of the engine casing as it extends into the engine. These contact points may orient that free end of the dipstick such that it doesn't contact a wall of the engine casing. Furthermore, these contact points may change the vibration characteristics of the dipstick. For example, the contact points may reduce the unconstrained portions of the dipstick and the dipsticks vibrational frequency.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.